Washington also received right-hander Rob Gilliam in the deal. According to a source, the Nats were going to trade pitcher Cole Kimball as part of the deal. Instead, Cole was added to the package.
Getting Gonzalez was a top priority for the Nationals after they were unable to reel in left-hander Mark Buehrle, who signed with the Marlins.
Gonzalez joins a rotation that will include Stephen Strasburg, Jordan Zimmermann, John Lannan, Chien-Ming Wang and Ross Detwiler.
"I love everything about it," Gonzalez said about the rotation via phone. "I remember growing up watching Chien-Ming Wang with Yankees. You are talking about great guys in that rotation. I don't want to step on anybody's toes. I want to be a part of it as much as possible.
"Hopefully, when I break into camp with these guys, it's going to be fun. Our hard work from the offseason is going to pay off during the regular season."
Last season, Gonzalez was 16-12 with a 3.12 ERA and had 197 strikeouts in 202 innings. He will not be a free agent until after the 2016 season.
"I feel great. It's a positive thing the Nationals pulled trigger and they gave me the opportunity to go to the National League and try to compete for a playoff spot and a World Series," Gonzalez said. "After talking to [general manager] Mike Rizzo and the way he sounds, I think this is perfect. He sounds like a guy who is putting the pieces together. He wants to compete and win a title. Those are the people you want to play for."
"[A's general manager] Billy Beane was great with what he did for me, sending me to Washington. He thought it was a great idea. He knew how important it was for them over there. I appreciate what Billy did and what the Nationals have done for me now."
In Gilliam, Washington gets a right-hander who was 12-7 with a 5.04 ERA for Class A Stockton. He struck out 156 batters in 164 1/3 innings.
As for the players the Nats gave up, Peacock was arguably the organization's best pitching prospect. He went 15-3 with a 2.39 ERA for Double-A Harrisburg and Triple-A Syracuse this season. Peacock was promoted to the Majors late in the season and allowed one run in 12 innings.
Norris was Washington's top catching prospect, but he is coming off his worst season, hitting .210 with 20 home runs and 46 RBIs. Norris said that the trade was unexpected, but he understood why it was made.
"You don't wake up every day and find out you were part of a [six]-man trade for a big leaguer. I feel like if they made that trade for us, that means they obviously means they like us," Norris said. "They obviously see a future for us. I'm not saying the Nationals didn't. If someone is willing to give up a guy like Gio Gonzalez for a few Minor League prospects, I feel they have a good plan for us and I'm excited."
Milone was consistent this year, going 12-6 with a 3.22 ERA for Triple-A Syracuse before receiving a promotion. He has the distinction of homering in his first big league at-bat against the Mets in September.
Cole was selected in the fourth round of the 2010 First-Year Player Draft. In 20 games for Class A Hagerstown this year, he was 4-7 with a 4.04 ERA.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.